1. Field of the Invention
The present invention relates to an injector for an engine, and more particularly, to the structure of an electronically controlled injector that can appropriately inject fuel in accordance with the operational conditions of the engine by changing the fuel injection types in various ways.
2. Description of Related Art
Electronically controlled injectors of the related art have a solenoid valve in the body and inject fuel by electrically controlling the solenoid valve to operate a needle and open a nozzle hole.
As the difference in diameter at the inlet and the outlet of the nozzle hole changes, the injection type of fuel injected through the nozzle hole changes, and the injection type of fuel can be divided into a type that is advantageous in improving the output of the engine and a type that is advantageous in reducing harmful exhaust gas.
That is, when the diameter of the nozzle hole is smaller at the inlet than the outlet, cavitation occurs due to the fuel passing through the nozzle hole and fuel injection that is advantageous in mixing the fuel with air is implemented, such that it is advantageous in reducing fuel consumption and harmful exhaust gas. Further, when the diameter of the nozzle hole is larger at the inlet than the outlet, the fuel is injected without causing the cavitation, such that a larger amount of fuel can be injected and fuel injection that is advantageous for output of the engine.
However, the nozzle holes of the related art is formed in a predetermined shape at the lower end of injectors, such that they cannot changes the types of fuel injection appropriately in accordance with the operational conditions of the engine, as described above.
Further, the injector equipped with a solenoid valve, as described above, cannot achieve injection rate shaping, as compared in FIG. 1.
That is, the solid line in the graph of FIG. 1 show changes in the injection amount to time in the injector equipped with a solenoid valve of the related art, in which the shape is simple and other dotted lines in the graph show various injection types and is difficult to be implemented by the injector equipped with a solenoid valve of the related art.
Piezo injectors equipped with a piezo element have been used in the related art to variably implement the various injection types shown by the other dotted lines, not the solid line in FIG. 1, but the cost is high.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.